The present invention relates to a technique employable effectively for multistage high frequency power amplifier circuit devices, each having a plurality of semiconductor amplification elements connected in a cascade, as well as for such radio communication apparatuses as portable telephones, etc. in which such a high frequency power amplifier circuit device is built respectively. More particularly, the present invention relates to a technique for improving the controllability of an output power (gain) with use of a power control signal voltage of the high frequency power amplifier circuit device and the efficiency of the device at a low power output.
In such radio communication apparatuses (mobile communication apparatuses) as mobile telephones, portable telephones, etc., a multistage high frequency power amplifier circuit device is built in the transmission side output stage respectively. The high frequency power amplifier circuit device includes semiconductor amplification elements such as MOSFETs (Metal Oxide Semiconductor Field-Effect-Transistors) and FaAs-MESFETs, etc., which are connected in a cascade. In the high frequency power amplifier circuit device, the semiconductor amplification element in the last stage is usually composed of discrete parts (an output power MOSFET, etc.) and the semiconductor amplification element in the preceding stage and the bias circuit are often integrated into a semiconductor integrated circuit formed on one semiconductor chip. Hereinafter, a component in which a semiconductor integrated circuit that includes semiconductor amplification element parts, the bias circuits, capacity elements, etc. are integrated will be referred to as a high frequency power amplifier module or simply as a module.
And, a portable telephone system is generally configured so as to change the output (transmission power) according to the ambient conditions with use of a power level command signal received from a base station so as not to cause radio interference in the communications with another portable telephone. For example, in the case of the cellular portable telephone such as the 900 MHz band standard method employed in the United States of America, the GSM (Global System for Mobile Communication) method employed in Europe, etc., the high frequency power amplifier module in the transmission side output stage is configured so that the gate bias voltage of each output power element is controlled so as to output a power required for talking with use of the output voltage Vapc of the APC (Automatic Power Control) circuit.
In addition, for a portable telephone, employment of a high efficiency high frequency power amplifier module is a very important factor for deciding a talking time and a waiting time, that is, an operating life of the battery. This is why the performance of the mutual conductance, etc. among the semiconductor amplification elements of a module has been improved to achieve such the high efficiency.
Japanese Patent Application No. Hei 11(1999)-275465 discloses a radio communication apparatus in which a multistage high frequency power amplifier module is built. The module includes a plurality of MOSFETs that are connected in a cascade. This radio communication apparatus improves the controllability of the output power Pout (to suppress an increase of the Pout with respect to an increase of the Vapc, that is, ΔPout/ΔVapc) with use of bias means provided to generate a gate bias voltage Vg so as to minimize the variation of the output power Pout with respect to the Vapc around the threshold voltage Vth of the MOSFET in each amplification stage according to the power control signal voltage Vapc generated on the basis of its body power control signal.